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Film / Forbidden Planet

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"See androids fighting
Brad and Janet!
Anne Francis stars in
Forbidden Planet!"
— "Science Fiction, Double Feature", The Rocky Horror Picture Show

Forbidden Planet is a 1956 Science Fiction film directed by Fred M. Wilcox, written by Cyril Hume, and starring Walter Pidgeon, Anne Francis, and a pre-Airplane! Leslie Nielsen.

How to best sum up its plot? Think Shakespeare... IN SPACE!

Loosely adapted from The Tempest (with a few nods to H. P. Lovecraft's At the Mountains of Madness), Forbidden Planet tells the tale of an Earth rescue mission to the planet Altair IV in order to determine the fate of the starship Bellerophon, which landed an earlier expedition. United Planets Cruiser C-57D, piloted by Commander John J. Adams (Nielsen), arrives to find that the Bellerophon's sole survivors are Dr. Edward Morbius (Pidgeon), his daughter Altaira (Francis), and their robot house servant, Robby. Adams's investigation into the mystery reveals secrets that can change the course of human civilization but unleashes a hideous monster in the process.

A classic of '50s sci-fi cinema whose story, production values, and special effects hold up well even by today's standards. It is the first film whose soundtrack consists entirely of electronic music and which was written for magnetic tape (and it was made by a couple, Louis and Bebe Barron).

By the way, if you watch this film and can't help but think it feels completely like a Star Trek episode (but without Mr. Spock), that's no accident — Gene Roddenberry fully admitted that Forbidden Planet was one of the primary inspirations for his series, and Forbidden Planet's fingerprints are all over Trek's writing, story, style, and tech, especially the original pilot episode, The Cage. It also gave some Japanese creators their momentum, and its elements can be found again in Space Battleship Yamato and Space Runaway Ideon.

It spawned a Jukebox Musical version called Return to the Forbidden Planet which hit its popularity in the '90s, winning an award and gaining a slight cult following.

This film provides examples of:

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    Tropes A-M 
  • Absent Aliens: The Krell have been extinct for millennia by the time the story takes place. No physical evidence of their appearance seems to have survived, the only hints being the triangular doorways in Morbius' complex, the knee-high safety railings, and the greater width of a headset's connector-arms.
  • Adaptational Villainy: Shakespeare's Caliban is by and large a Harmless Villain who realizes his folly and is reconciled with Prospero at the end of The Tempest. The Id Monster is an unstoppable force of destruction that Morbius must take his own life to defeat.
  • Alien Sky: Altair IV has a green sky and two moons.
  • All Girls Want Bad Boys: Altaira is warned that the captain can't be trusted with women, and she promptly zeroes in on him.
  • All Men Are Perverts: Invoked on two occasions.
    • The XO, in an attempt to get Altaira for himself, implies that his captain and the ship's doctor can't be trusted alone with women. He then proceeds to prey on her innocence to introduce her to kissing. Altaira is unimpressed with kissing until she tries it with the captain.
    • The Captain attempts to justify his crew's behavior by noting they are all in superb physical condition, average 24.6 years old, and have been cooped up on the C57D for 13 months. Mind you he need not apologize. Altaira is thoroughly enjoying herself.
  • All Planets Are Earthlike: Downplayed; no "survival suits" are required, but the captain points out the gravity is slightly less and orders everyone to adjust their equipment accordingly, and the oxygen content 4.7% richer.
  • Artificial Gravity: One of the few movies where they switch it off before landing on a planet.
  • Artistic License - Food Hygiene: Cookie never removes his apron, even when he leaves the ship. This makes it much easier to tell him apart from all the other white men in uniform, but is not best practice for food hygiene. As well as protecting your clothes from the food, the apron also protects the food from your clothes. By never removing it, he risks bringing outside dirt into the kitchen. Alien outside dirt. That said, food hygiene seems like something that Cookie might not care too much about.
  • Artistic License – Physics: Nothing could survive three billion electron volts? Really? Tissue paper could withstand far more than that! The thermal energy sucked out of your skin when a snowflake melts on it is about a billion times higher. A common misconception is that "electron volt" is the same as a regular volt. Actually, it's the energy gained by a single electron accelerated through an electric potential difference of one volt. This is an incredibly tiny amount of energy. Alternatively,the three billion electron volts could be the energy in each particle, which is absurd in the other direction, being roughly three thousand times the energy of a gamma photon. The decay of a single gamma photon into visible light can be very easily observed with the unaided eye.
    • Electron volts can also be used as a measurement of temperature. Using this formulation, 3 GeV is equivalent to a temperature of around 35 trillion degrees Kelvin, so the statement makes sense.
  • As You Know: Commander Adams gives a shipwide broadcast telling the crew why they're going to Altair IV, even though he specifically mentions they've been given briefing lectures on the subject.
  • Belligerent Sexual Tension: The captain and Altaira.
  • Big Dumb Object: The vast self-powered Underground City of the Krell qualifies. Standing in one of the huge ventilation shafts, Dr. Morbius says that the platform they're standing on runs for twenty miles in either direction, and there's 7800 levels above them. And there's 400 other shafts like it.
  • Big Red Button: Actually a switch, that activates the countdown on the Krell planetary Self-Destruct Mechanism.
  • Bittersweet Ending: Morbius dies, but he manages to stop his runaway Id from destroying his daughter. And the Forbidden Planet explodes, taking the unimaginably advanced science of the Krell with it. True, the protagonists manage to keep Robby, who is stated to be beyond state of the art, but Krell technology is thousands of years ahead of anything we have, and just from what we see they could have revolutionized agriculture, power generation and metallurgy to such a degree that it would have been one of the most important discoveries in human history. Then again, even the Krell, in all their development, ultimately proved unable to wield such power without self-destructing, and they had longer to get used to it.
  • Bloodless Carnage: The battle with the Id Monster, considering it had the weapons and strength to tear anything that got too near it limb from limb (as was revealed in a Gory Discretion Shot earlier). It was already pushing the boundaries for a 1950s sci-fi movie; hard to fault it for using this trope.
  • Breakout Character: Robby the Robot. Robby was re-used in many subsequent sci-fi movies and even television programs not only due to his popularity but also to recoup the tremendous cost of constructing him.
  • Calling the Old Man Out: Altaira was reluctant at first to leave with the crew, as she doesn't want to leave her father and still believes she and her father are immune to the monster. Until she sees he has no sympathy for Lt. Ostrow, calling his death karma for his own "greed and folly".
    Morbius: The fool, the meddling idiot. As though his ape's brain could contain the secrets of the Krell.
    Altaira: Morbius... you wanted me to make a choice. Now you've chosen for me.
  • Character as Himself: Robby the Robot is billed in this manner. (He was actually operated by Frankie Darro and voiced by Marvin Miller.)
  • Covers Always Lie: See that poster up there? The robot's not the bad guy. And he never carries the woman like that, although he does carry a dying man that way at one point. The woman in the poster isn't a very good match for Altaira either. The poster was most likely a Shout-Out to pulp science fiction magazines like Amazing Stories.
  • Crystal Spires and Togas: The Krell, before the destruction of their civilization, lived in "cloud-piercing towers of glass and porcelain and adamantine steel," and their culture had apparently all-but destroyed problems of prejudice and poverty. By the time the humans get there everything above ground has all crumbled into dust.
  • Curb-Stomp Battle: The one time that the humans are prepared for the arrival of the Id Monster makes not the slightest difference as it tears through weaponry, shields and Red Shirts like tissue paper. Each time they score a hit, the Krell machinery just adds another 10x more energy to it .. and it keeps on coming.
  • Deadly Upgrade: The doctor uses an Upgrade Artifact to rapidly become smart enough to learn the planet's secrets, but dies in the process. Earlier, Morbius did the same thing and survived, but he took his time, and even then... well, see below.
  • Deadpan Snarker: Robby to a certain extent.
    Commander Adams: Nice climate you have here. High oxygen content.
    Robby: I rarely use it myself, sir. It promotes rust.

    Altaira: Robby, I want you to run up a new dress for me.
    Robby: Again?
  • Death of the Hypotenuse: Lieutenant Jerry Farman, which eliminated any possibility that he could interfere with Adams and Altaira getting together.
  • Disproportionate Retribution: After the invisible monster lifts the hatch, a man sleeping nearby rouses slightly, but sees nothing so thinks he's dreaming and goes back to sleep. The next day Adams docks his space pay even though the man wasn't even on guard duty.
  • Distracted by the Sexy: Happens to all the crewmen who meet Altaira, who is Obliviously Beautiful and can't understand why being so friendly and outgoing might fuel some male predatory behavior. Commander Adams isn't immune to it himself and he reads her the riot act about how distracting she is to all the men. Altaira tries to have a concealing dress made to avert this, but utterly fails to make Altaira look frumpy and instead makes Adams even more attracted to her than before.
  • Do-Anything Robot: Robby, an early example. He is incredibly strong, has a vast database, is a Matter Replicator, and although he can't hurt humans, he can disarm them, and has some kind of stinger ray for shooing away animals.
  • Eating the Eye Candy: Altaira is clearly thrilled at having a whole shipload of hunky spacemen to choose from and eager to gain experience.
    "You're lovely, Doctor, but the two on the end are unbelievable!"
  • Eldritch Abomination: The Id Monster. It doesn't drive people insane (more feeds off their inner insanity), but it's utterly unlike anything living. It's loaded with (un)natural weapons quite capable of shredding anything that gets in its way. Worst of all, the Krell machinery feeding it gives it effectively infinite strength. Nothing will stop it from reaching its intended target and destroying it except its originator's Heroic Sacrifice.
  • Enemy Without: Coupled with Unstoppable Rage, Morbius' id can use the Forgotten Phlebotinum that runs the planet's machines to create a monster literally born of jealousy and possessiveness to deal with intruders, which his conscious self is powerless to stop.
  • Eternal Engine: The Krell machinery, which was underground, 20 miles long per side, in the shape of a cube, and full of fusion reactors.
  • "Eureka!" Moment: After the id monster's attack on the ship, Adams and Doc Osgrow discuss how it could withstand their weapons, and the Doc reasons that it was regenerating itself "from one microsecond to the next!" The phrasing gives Adams the key clue to the monster's source (Morbius said the same thing about a mental projection he'd showed them, made with the Krell machinery).
  • Exact Words:
    • Altaira is told by papa not to go near the ship, so she just parks nearby. "After all, this isn't very near." He earlier tells her not to turn up for lunch, so just turns up for coffee afterwards.
    • In a secondary example, Cook "sneaks out" of the ship to obtain 60 gallons of liquor from Robby the Robot at their meeting place amidst the rocks. While engaged in conversation with Cook, Robby pauses and scans the area, causing the human to ask if someone's "coming this way", which Robby reassures him is not the case. An invisible monster proceeds to sneak aboard the ship and kill a crew member.
  • Explain, Explain... Oh, Crap!: Subverted at first, as Morbius was in denial of the obvious.
    Morbius: The last Krell died 2,000 centuries ago. But today, as we all know, there is still at large on this planet a living monster.
    Adams: Your mind refuses to face the conclusion.
  • Expy: The main characters mirror the main characters of The Tempest: Morbius is Prospero, Altaira is Miranda, Robby is Ariel, the Id Monster is Caliban, the Captain is Ferdinand, and the Krell serve the position of Sycorax. Cook and Trinculo both serve as drunken comedy relief.
  • Failed Future Forecast: Men and women in rocketships have reached the Moon by the end of the 21st Century (though in fairness, we're still waiting for that Woman in the Moon).
  • Flying Saucer: This time the humans have one (the United Planets Cruiser C57D, said to be the inspiration for the saucer section of the U.S.S. Enterprise).
  • Fourth-Date Marriage: Late in the movie Altaira absolutely refuses to deny her love for the Captain, even though they've known each other for like three days by that point.
  • Friend to All Living Things: Altaira, until she first feels sexual desire, at which point it shuts off like a light switch.
  • Future Music: Alleged to be the first film with an all-electronic score.
  • Future Society, Present Values: The opening narration seems to imply a certain amount of equality in the future... and then immediately shows us a crew made up entirely of white men. The attitudes of said white men towards Altaira are also noticeably very 1950s, particularly the attitude towards her skimpy outfits. There's even one point where Commander Adams tells Altaira to start covering herself (because it's her responsibility to keep the men from ogling her), and she has Robby make her a new dress because just putting on a pair of pants would be unthinkable. However, those attitudes were somewhat justified because, when the film was made, Sputnik I hadn't been launched into orbit yet and no one knew if someone could survive both the Zero-G of outer space and the G-forces of an orbital rocket launch or atmospheric re-entry. The requirements for the first group of American astronauts was for military test pilots with large amounts of jet experience ... which excluded most male American pilots and all female American pilots.
  • Get Thee to a Nunnery: Id Monsters, for that fizzy sweet apocalyptizing goodness.
  • Ghost Planet: The planet Altair IV is essentially this, with just Dr. Edward Morbius and his daughter living there.
  • Gone Horribly Right: The last invention of the Krell was evidently meant to be an improvement over their Matter Replicator technology that would allow them to give form and substance to anything they could imagine without having to feed a sample of it into a machine for analysis first. As the ship's doctor Lt. Ostrow concludes, their new device was a smashing success at this, but it also Dug Too Deep in a psychological sense: the Krell forgot about the irrationally evil and violent desires lurking deep in the subconscious imagination of every rational being, to which their new device also gave form and substance. These "monsters of the id" then destroyed their civilization and exterminated them all, and came close to doing the same to all the humans on the planet after Dr. Morbius took to fiddling with it.
  • Good Cannot Comprehend Evil: "My poor Krell. After a million years of shining sanity, they could hardly have understood what power was destroying them."note 
  • Good Hair, Evil Hair: Dr. Morbius' goatee pegs him as close to evil, while Adams and co. are clean shaven to the point of being shiny. Subverted eventually, however. Morbius isn't evil, just human. And his better nature ultimately wins out.
  • Gory Discretion Shot: The Id Monster sneaks into the ship at one point and absolutely shreds the first crewman it comes across. The captain's description of the remains may seem almost quaint compared to modern horror standards, but for a 1950s audience it must have been pure Nausea Fuel.
  • Ham-to-Ham Combat: When monster attacks the house, Leslie Nielson goes full Captain Kirk and Walter Pigeon puts on his best Tragic Trek Villain as they argue over the source of the Krell monster.
  • Have a Gay Old Time: Dr. Morbius says that his enhanced intellect, by the standards of the Krell, would be comparable to that of a "low-grade moron," which at the time was a technical term for someone with an I.Q. in the 51-70 range.note 
  • The Heartless: The id monster.
  • Heroic Sacrifice:
    • Knowing that the Krell machine could kill a human using it, Lt. Ostrow runs off when Commander Adams is distracted to use it. This could be hubris and him wanting to use it first (Commander Adams had insisted he go first), or taking the risk on himself to spare his captain. Either way, he lives just long enough to reveal the nature of the id monster and provide the means of saving everyone.
    • Once he realizes that the id monster is him, Dr. Morbius begs Commander Adams to kill him to save his daughter. He then confronts the monster directly, resulting in his death.
  • Homage: Besides the tributes listed above, creatures similar to the id monster have appeared in series as diverse as The Outer Limits (1963) ("The Man with the Power") and My Little Pony: Friendship Is Magic ("All Bottled Up").
  • Horny Sailors: The crew of the spaceship is all-male and stir-crazy from a long flight, and respond energetically when they come across the Mad Scientist's Beautiful Daughter. Two of the ship's officers start a Cock Fight over her. As the phrase goes, Space Is an Ocean.
  • Humans Are White: Apparently only white people are sent on interstellar journeys, because there is no evidence of any other races on the ship.
  • Incredibly Lame Pun: Id Monsters, for that fizzy sweet apocalyptizing goodness.
  • Inertial Dampening: When their spacecraft decelerates on the approach to Altair IV, the crew stow their breakable gear and step into their "D.C. stations" which presumably neutralise their inertia.
  • Innocent Fanservice Girl: Altaira, being completely unaccustomed to normal social mores. (Though if you look when she gets out of the water you can see she's wearing a flesh colored suit).
    Altaira: "What's a bathing suit?"
  • Justified Trope: Why is the self-destruct device so easy to access? Because everyone on the planet was (externally) morally perfect.
  • Let Me Get This Straight...: Commander Adams sarcastic summing up of the report by the two sentries and a sleeping soldier who failed to see the Invisible Monster.
  • Logic Bomb: Robby's "built-in safety factor": he is compelled to obey Morbius, but is also compelled not to harm a rational being, and he shorts out if those two mandates come into conflict. Backfires when Morbius, in a panic, orders Robby to kill the Monster, and trips the failsafe instead, because Robby realizes that the Monster is being generated by the Krell machine from Morbius' own subconscious. The only way for Robby to kill the monster is to kill Morbius, which the failsafe will not allow, causing Robby to freeze up and be unable to take any action.
  • Lost Technology: The Krell, an alien race who lived on the titular Planet but died out hundreds of thousands of years ago, left behind an artifact that could dramatically boost the intellect of those few primitive, backward humans who survived the process. Their machines could also read the thoughts of those who used the artifact, and even cause some of those thoughts to become reality.
  • Made of Indestructium: During their tour of the Krell city, Dr. Morbius has Commander Adams try out his blaster on a door made of 26 inches of molecular-condensed metal; the beam doesn't even warm it up. However when Morbius tries to use those same doors to hold off the ID Monster it's to no avail, because the monster can draw on as many of the city's thermonuclear generators as it needs to burn through it.
  • Mad Scientist: Lampshaded by Dr Morbius after demonstrating that Robby is Three Laws-Compliant; even if he was the proverbial mad scientist of the "tape thrillers", he could not possibly harm anyone with the technology he has. Turns out he has other attributes of a mad scientist like hubris, lack of self-awareness, and a failure to think things through.
  • Mad Scientist's Beautiful Daughter: Altaira's father, Dr. Morbius, keeps her completely isolated from the social world outside Altair IV.
  • Mars Needs Women: The poster of Robby carrying Altaira. Once you know he's harmless, it tends to lose its impact.
  • Meaningful Background Event: Coupled with Foreshadowing; During the id monster's big attack on the C57D, the film inserts a shot of Morbius sleeping (and having a nightmare) in the Krell lab; behind him, the energy gauges of the Krell machinery are lighting up one after the other, and darken once he awakens. The same thing happens later during the climax in that same lab, when Adams is trying to convince Morbius of the monster's true source, with the gauges lighting up one by one as the monster tries harder to get through the door until the entire wall is lit up.
  • Meaningful Name:
    • Morbius is very close to "Morpheus", the Greek god of sleep. And what happens when Morbius sleeps? It's also close to "morbid", and Morbius is obsessed with studying a dead civilization.
    • Altaira is apparently named after the planet she was born on - Altair IV. Her name probably says more about her father than it does about her character.
  • Mental Monster: The monster that killed most of the crew of the starship Bellerophon was formed by the equipment left by the Krell, evidently meant to be an improvement over their Matter Replicator technology that would allow them to give form and substance to anything they could imagine. The equipment, however, also gives form and substance to irrationally evil and violent desires lurking deep in the subconscious imagination of every rational being, and the monster the protagonists face is really the Id of Dr. Edward Morbius.

    Tropes N-Z 
  • Never Split the Party: Subverted; Farman lets Cookie go outside the energy fence on an errand that even he can tell is bogus. At one point Cookie has the requisite falling on his face and looking up to see...not a terrible monster, but Robby with a huge pile of bourbon bottles. While he's busy, the invisible monster simply walks through the fence to attack those inside.
  • Never Trust a Trailer: See the poster up at the top? Not only does the depicted event never happen, it's intentionally misleading. (There is a notable Robby fake-out in the movie that works better if you've seen the poster).
  • No Seat Belts: Averted when Robby tells them to buckle up before driving a vehicle at his speed. And it's not necessary for the spaceship because they have Inertial Dampening.
  • No Man Should Have This Power: Dr. Morbius insists that humanity won't be able to handle the power granted by the Krell artifacts. Captain Adams resents Morbius setting himself up as the arbiter of this technology; when Morbius himself can't handle the power, Adams realizes this really is too much power for humanity, so he doesn't object to destroying the entire planet.
  • No Name Given: The cook is never named.
  • No OSHA Compliance: Justified; while the railings of the bridges spanning the massive ventilator shafts are below knee height, the Krell are implied to be a lot shorter and squatter.
  • Nothing Is Scarier: Most of the appearances by the id monster feature... well, nothing. The creature is invisible unless 'colored' by some sort of energy (IE, the perimeter fence, blasters, etc). In fact, the only thing seen during its entire first "appearance" is footprints in the dust and dented stairs when it enters the ship, although one crewman can hear its breathing.
  • Not So Above It All: Commander Adams initially tries to protect Altaira from the lewd advances of his crew, but is not impervious to her charms himself.
  • Only Six Faces: The space crew can seem this way, since they're all clean shaven, brown-haired men with similar haircuts and identical uniforms (with the exception of the cook).
  • Outgrown Such Silly Superstitions: Apparently not.
    "The Lord sure makes some beautiful worlds."
  • Override Command: Altaira uses "Emergency Cancellation Archimedes" to get Robby to allow the captain and doctor into the house against her father's orders.
  • Papa Wolf: A shipload of sex starved spacemen sniffing around his daughter has Morbius understandably upset. It also brings out Morbius's long-dormant 'creature from the id,' eventually endangering even her with its unreasoning possessive rage.
  • Perilous Power Source: The Krell cube's power source, sunk into the planet fifty miles below the machine itself, is filled with 9200 thermonuclear reactors. Morbius shows them the inner workings, but only through a heavily filtered mirror. "Man cannot behold the face of the gorgon and live!" ("Gorgon Gazing" was even the former trope name).
  • Pietà Plagiarism: Robby carrying Altaira in the poster. In the actual movie he does carry a dying man this way.
  • Planetary Core Manipulation: The ancient Krell machine was powered by energy from the planet's core, and when the planet is destroyed in the end, it's done by setting off a chain reaction at the core.
  • Please Put Some Clothes On: Captain Adam's reaction to Altaira's being exposed while swimming.
  • Plunger Detonator: The Self-Destruct Mechanism that destroys the planet is a rod (minus the horizontal handle) that rises up from the floor; it is pushed down again to activate it, lighting up a Big Red Button in the process.
  • Precursors: The Krell. The movie only gives vague hints on what they might have looked like. The doors are much wider at the base than human doors, the teaching device is designed for something with a head much larger than a human's, and the railings along the catwalks in their huge machine are at about knee height for humans.
  • Properly Paranoid: There are some lessons here that could have been learnt by Star Trek away teams, like deploying a security team before allowing the officers to disembark, setting up an energy fence perimeter, and having a camera attached to your communicator to confirm you're not speaking under duress.
  • Ragnarök Proofing: Subverted. Krell stuff was built to last, as the underground complex beneath Morbius's house demonstrates, but, in the words of Doctor Morbius, "...seemingly on the threshold of some supreme accomplishment which was to have crowned their entire history, this all-but-Divine race [the Krell] perished in a single night. In the two thousand centuries since that unexplained catastrophe, even their cloud-piercing towers of glass, and porcelain, and adamantine steel have crumbled back into the soil of Altair IV, and nothing, absolutely nothing remains above ground." The Krell machine and its laboratory remained intact and functioning because it was designed and built that way with the ability to self-repair and self-maintain itself.
  • Raygun Gothic: One of the definitive examples; Robby the Robot in particular came to be iconic of the style.
  • Reality Has No Soundtrack: Instead of a conventional score, the film uses electronic sounds to suggest an otherworldly atmosphere. Hollywood composers, following the town's usual treatment of new styles and ways of doing things, panicked that these electronic musicians would put them all out of work, and had the couple that produced the music blacklisted for the rest of their careers.
  • Reverse Polarity: Used by name by the C-57D's crew during the landing process on Altair 4.
  • Robot Antennae: Robby the Robot has two asymmetrical circular antennae as "ears."
  • Robot Buddy: Robby is perhaps the Ur-Example of this trope. Polite, friendly and helpful, though occasionally droll and sarcastic (but never malicious), it's little wonder why he was the breakout star of the film, especially when you see him just standing around getting drunk with the C57D's cook.
  • Robot Names: The classic "Robby the Robot" even alliterates!
  • Roger Rabbit Effect: The id monster, during his on-screen appearance, which was animation done for the film by Disney animator Joshua Meador.
  • Say My Name: Altaira calls her father "father" throughout the film until she decides to leave, at which point she calls him "Morbius".
  • See the Invisible: The monster's tracks can be seen, and its outline becomes visible when it moves between the energy-fence's pylons or has raygun fire splash off of it.
  • Self-Destruct Mechanism: At the end, destroys the planet and all the knowledge of the Krell.
  • Self-Healing Phlebotinum: Said of the Krell machines.
  • Servile Snarker: Robbie the Robot draws on the ancient tradition of snarky butlers and other house-servants.
  • Setting Update: Shakespeare's The Tempest, IN SPACE! Famously, this took the form of updating the magic of the original into scientific concepts, like Morbius being a scientist rather than a magician and using Freud's theories of the elements of the unconscious mind rather than the classical elements of the natural world, and associating the moral, logical superego with Robbie the Robot while the Monster from the Id represents the unfettered, mindless impulses and drives of the mind in the same vein as Ariel's association with air and fire while the brutish Caliban is connected to the "lower elements" of earth and water.
  • Scotty Time: Played with when the Chief shows Commander Adams the busted Subspace Ansible. He acknowledges that repair is impossible...and wants to know how much time will it take. The Chief just quips, "Well if I don't stop for breakfast..."
  • Starfish Alien: The Krell are never shown, but they are clearly not humanoid, based on the tools and furnishings they leave behind.
  • Stealth Insult: After his daughter complains about Commander Adams shouting at her for no reason that she can understand, Morbius has Adams try out the Krell IQ test for children and isn't surprised at the low result, because all a commander has to have is a loud voice.
  • Stealth Sequel: Robby the Robot was so popular that he appeared as the co-star in a B&W children's movie called The Invisible Boy. In an application of this trope, the movie was implied to take place in the same universe as Forbidden Planet, with Robby being pulled back in time to the present day by a scientist's experiment. Some releases of Forbidden Planet include The Invisible Boy as DVD Bonus Content.
  • Supering in Your Sleep: Dr. Morbius.
  • Technobabble: It didn't start with Star Trek. At least here it's just to add a technological sheen, rather than a plot device.
  • Technology Porn: Has the requisite "showing off the wonders of alien technology" scenes that would be done far less smoothly in Follow the Leader sci-fi movies of the 50s and 60s.
  • Thou Shalt Not Kill: The robot is programmed to shut down should he be ordered to harm any "rational being". This feeds directly into a Logic Bomb, when the robot is ordered to do exactly that, though this is to demonstrate that he is harmless and friendly to an audience used to more-traditional robots.
  • Three Laws-Compliant: Robby, most definitely. We're shown very early that he cannot harm humans, and that he will obey any order other than to kill. This becomes a plot point, later, when Morbious orders Robby to destroy the monster, only for Robby, who knows the truth of the monster, to freeze up, unable to comply. This is part of what convinces Morbious at last of the truth of his link to the monster.
  • Too Dumb to Live: When the monster attacks and kills two men who get too close, while showing itself to be completely unaffected by their weapons, Jerry Farman runs forward (into the line of fire of the others, forcing them to cease fire) to continue shooting at it at point-blank range. His subsequent death is both utterly predictable and utterly pointless.
  • Touch of the Monster: The above poster — though subverted as Robby is the resident Robot Buddy.
  • Tulpa: The Id Monster is this to Morbius.
  • Virgin Power: Altaira's communion with the animals. She loses the ability as soon as she starts to enjoy kissing Commander Adams. Rather than a Garden of Eden allegory, it represents her jealous father's internal resentment of her leaving him.
  • What Did You Expect When You Named It ____?: The ship that originally brought Morbius to Altair IV is called the Bellerophon. In Classical Mythology, Bellerophon was a great hero who tamed the Pegasus. However, he also fell victim to hubris, and was punished by being sent crashing down to Earth from his mount, where he died a blinded cripple.
  • What Is This Thing You Call "Love"?: The crew is eager to demonstrate the human custom of "kissing" to Altaira. She is initially unimpressed, but quickly warms up to it.
  • White-and-Grey Morality: Morbius: it implies that even the worst people have good intentions.
  • Worthless Yellow Rocks: Robby has no problem whipping up a dress for Alta overnight using 5-to-15 carat diamonds which he has on hand.
  • You Are Not Ready: Morbius' dictum that he would parcel out the dead planet's Phlebotinum as he saw fit so as not to corrupt humanity. Eventually, The Captain agrees with him that none of it should be used by anyone else, and the planet is made to self destruct. On the other hand, the crew does bring a fully functional AI robot with superhuman strength and an on-board Matter Replicator back with them, so the Krell tech certainly wasn't all destroyed.